(a) Field of the invention
The present invention relates to an electronic image pickup device for endoscopes, which is suitable for being provided in a compact size.
(b) Description of the prior art
There have been proposed in recent years various types of electronic image pickup devices for endoscopes using such devices as solid-state image sensor to serve as an image pickup device.
The above-mentioned electronic image pickup device for endoscopes using a solid-state image sensor has such an advantage that it is capable of preventing the degradation of the quality of images accruing from the breakage of those optical fibers used in an endoscope which employs an image guide formed with an optical fiber bundle, or an advantage that the recording, etc. of the picked-up images becomes easy. Along therewith, a further reduction of size and a further improvement of the resolving power of images to be picked up can be envisaged, so that such an endoscope equipped with an image pickup device made of a solid-state image sensor is going to be used progressively widely from now on.
An electronic image pickup device for endoscopes of the type as mentioned above which is disclosed in, for example, Japanese Utility Model Preliminary Publication No. Sho 61-159901 provides an apparatus characterized by comprising an endoscope equipped with a line-sequential transmission type solid-state image sensor which is disposed within the forward end portion of the endoscope to be operative so as to receive an optical image coming from an object under observation and to convert the optical image thereof to an electric signal, and also equipped with a light-transmitter which receives, at its light-incidence end face, the light coming from a light source and which leads this light to a light-emitting end face thereof provided at the forward end portion of the endoscope to thereby illuminate the object under observation, and further comprising a filter disc disposed between said light source and the light-incidence end face of said light transmitter and having, formed on a same circumferential face in an alternating fashion, a light-blocking area for blocking the light beam coming from the light source and also having light-beam-transmitting areas for transmission therethrough of at least three different kinds of color lights, respectively, whereby the apparatus is operative so that, by rotating the filter disc at a constant speed, said at least three different kinds of color lights will successively illuminate the object under observation with an interval of time corresponding to the light-blocking period between respective such illuminations, thereby reading out during each light-blocking period the electric charge accumulated in said solid-state image sensor and converting the thus read-out electric charge to an electric signal, to perform a display of a color image of the object under observation based on such electric signals. In addition, the apparatus is further characterized in that the opposing ends of said light-transmitting areas and the diaphragm which is provided on the light-source side away from said light transmitter are each formed to have such a configuration that a constant time period of passage of the light-blocking area can be maintained during the revolutions of the filter disc for those light beam-transmitters which could have different diameters.
However, the above-described conventional electronic image pickup device for endoscopes is exclusively aimed to perform observations by the use of only visible light, and thus it has been impossible to conduct observations utilizing invisible light.